The present invention relates to a repair and reinforcement method for preexisting structures such as bridge columns, piers, bridges, and buildings, and in particular, relates to a repair and reinforcement method for concrete structures, and to an anisotropic textile used in this method.
The repair and reinforcement of preexisting structures comprising concrete such as bridge columns, piers, bridges, and the like by the use of a unidirectional sheet material, in which carbon fibers, glass fibers, or high strength organic fibers are arranged in one direction, these are impregnated in advance with a small amount of resin, and are restricted in the weft direction and the thickness direction, or common textile materials, wherein these are affixed to the structures while impregnating with resin, and are then left to cure, is generally known.
In this case, cold-curing type epoxy resins, which have a long period of use and are comparatively easily handled, are most broadly employed as the matrix resin which is impregnated into the sheet material.
Furthermore, repair and reinforcement methods are also known in which, in order to shorten the work period at the site and to obtain stable properties, a so-called prepreg, which has been impregnated in advance with an appropriate amount of resin, is affixed, and this is then cured.
However, when the cold-curing epoxy resin which is commonly employed as a matrix resin in this field is used, although this is termed a cold-curing resin, the curing properties decline markedly below 10xc2x0 C. and in particular below 5xc2x0 C. and this leads to defects in curing and this leads to a lengthening of the execution period.
On the other hand, there has been much consideration given to the use of reinforcing materials (hereinbelow referred to as sheet materials) which form fiber-reinforced resin with resin. When a textile material comprising common reinforcement fibers is employed, the fibers run in two directions, so that the strength in one direction is less than half, and this is extremely disadvantageous when strengthening is particularly to be carried out in one direction, so that the use of a variety of unidirectional sheet materials has been considered.
(1) Use of Reinforcement Fiber Bundles
A technique in which reinforcement fiber bundles are wrapped around spots to be repaired and reinforced in preexisting structures while resin is being applied thereto is disclosed in Japanese Patent Application, First Publication No. Sho 62-33973 and Japanese Patent Application, First Publication No. Sho 62-244979.
(2) Use of a So-called Prepreg in which Resin is Impregnated in Advance into Reinforcement Fibers
A technique in which a sheet material, in which a net-shaped material is applied to a prepreg, in which reinforcement fiber bundles are arranged and impregnated with resin so that the amount of resin contained is 15 weight percent or less, is applied to portions to be repaired or reinforced of preexisting structures, and curable resin is applied and impregnated from the surface thereof, is disclosed in Japanese Patent Application, First Publication No. Hei 7-228714.
(3) Use of Reinforcement Fiber Cloth in which Resin is Not Impregnated in Advance into the Reinforcement Fibers
A technique in which a screen shaped sheet material in which carbon fibers are woven horizontally and vertically is applied to spots to be repaired and reinforced of preexisting structures, and a curable resin is applied and impregnated from the surface thereof, is disclosed in Japanese Patent Application, First Publication No. Sho 63-201269.
(4) Use of a Material which can be Positioned Between That of (2) and (3) A technique in which a sheet material, in which arranged reinforcement fiber bundles are applied to a supporting sheet via an adhesive layer, is applied to spots to be repaired and reinforced of preexisting structures, and a curable resin is applied and impregnated from the surface thereof, is disclosed in Japanese Patent Application, First Publication No. Hei 3-224901, Japanese Patent Application, First Publication No. Hei 4-149366, and Japanese Patent Application, First Publication No. Hei 5-32804.
However, in technique (1) above, in order to impregnate the reinforcement fiber bundles with resin and to wrap these around spots to be repaired and reinforced, it is necessary to use a dedicated-wrapping machine, and work is required to bring this machine to the site, and it is also difficult to use such a machine at sites for repair and reinforcement having a variety of conditions.
Furthermore, the sheet material which is employed in the technique described in (2) above is a sheet-shaped material in which, in order to ensure good handling properties during the carrying out of repairs, slightly more resin is applied to the reinforcement fibers than in the case of the level of a common sizing agent, the gaps between fibers are restricted, and a further net-shaped body is laid thereon, so that it is difficult to impregnate resin thereinto at the site in a short period of time, and it is not easy to use resin having a short period of use.
Furthermore, in the technique of (3) above, in the same way as in the case of a common textile material, a flat support body which is made unitary through the application of an amount of resin or an adhesive layer is not used; however, because of the severe restriction of the space between the reinforcement fibers themselves, the impregnation of resin is not easy, and resin having a short period of use cannot be employed.
Furthermore, in the technique described in (4) above, the arranged reinforcement fiber bundles are attached to a planar support body comprising a non-woven cloth or a net-shaped textile via adhesive layers, and this is made unitary, so that it is difficult to impregnate the resin in a short time at the site, and resin having a short period of use cannot be employed.
Furthermore, when sheet materials such as those described in (2) and (4) above are employed, when a resin having a low viscosity and great dissolving power such as an acrylic monomer or unsaturated polyester resins is impregnated, the resin which is to be impregnated is impregnated while dissolving the resin which was previously deposited in order to restrict the fibers, so that the fiber orientation becomes chaotic during the execution of the procedure, and it is impossible to obtain sufficient strength.
The present invention solves the problems described in the conventional art above; it has as an object thereof to provide a repair and reinforcement method for preexisting structures which is capable of execution even in poor conditions such as low temperature, and which is capable of exhibiting superior repair and reinforcement effects in a short period of time, as well as to provide an anisotropic textile which has superior handling properties and resin impregnation properties, and which also generates superior strength when hardened.
The present invention comprises a repair and reinforcement method for preexisting structures, wherein, during the repair and reinforcement of preexisting structures using a fiber-reinforced resin layer in which resin is impregnated into a sheet material comprising reinforced fibers and this resin is cured, the resin which is employed is a reactive mixture having a gelling time at 20xc2x0 C. of 15 minutes or more and which initiates polymerization even at 5xc2x0 C., and is curable in a period of time 6 hours less even at 5xc2x0 C., and which has as the chief components thereof (1) a monomer having vinyl groups and (2) a reactive oligomer and/or a thermoplastic polymer having vinyl groups; and an anisotropic textile, having as the warp thereof a high strength and highly elastic fiber having a tensile strength of 3 GPa or more and a tensile elastic modulus of 150 GPa or more, and a fiber having a tensile elastic modulus lower than that of the warp as the weft thereof, wherein the weft comprises a compound thread having a weight of 0.1 g or less per one meter of fiber and comprising two types of fibers, the difference in the melting point of which is 50xc2x0 C. or more, the gap in the weft in the direction of the warp is within a range of 3-15 mm, and the warp and weft are caused to adhere to one another by means of the fiber having a low melting point comprising the weft.
The anisotropic textile of the present invention has superior handling properties and resin impregnation properties, and generates superior strength when cured, and is thus useful in the repair and reinforcement of preexisting structures.
Furthermore the repair and reinforcement method for preexisting structures of the present invention which employs this anisotropic textile and specified resins even in a sheet-form material comprising reinforcement fibers may be carried out in poor conditions such as low temperatures, and is capable of exhibiting superior repair and reinforcement effects in a short period of time.
First, the repair and reinforcement method for preexisting structures of the present invention will be explained.
In the repair and reinforcement method for preexisting structures in accordance with the present invention, during the repair and reinforcement of preexisting structures using a fiber-reinforced resin layer in which resin is impregnated into a sheet material comprising reinforcement fibers and cured, the resin which is employed is a reactive mixture (matrix resin) which has a gelling time at 20xc2x0 C. of 15 minutes or more and which initiates polymerization even at 5xc2x0 C., and is capable of sufficient curing in a comparatively short period of time (within 6 hours) even at 5xc2x0 C., and which, moreover, has as the chief components thereof (1) a monomer having vinyl groups and (2) a reactive oligomer and/or a thermoplastic polymer having vinyl groups, and this is affixed to the preexisting structure while impregnating the sheet material comprising reinforcement fibers with this resin, and this is allowed to stand and cure.
Examples of high strength or highly elastic fibers which may be employed as the reinforcement fibers used in the sheet material comprising reinforcement fibers include, for example, inorganic fibers such as carbon fibers, glass fibers, and the like, or organic fibers such as aramid fibers or the like, which are commonly employed as reinforcement fibers. Furthermore, if these reinforcement fibers are mixed it presents no problem.
Among these, high strength and highly elastic fibers having a tensile strength of 3 GPa or more and a tensile elastic modulus of 105 GPa or more are particularly preferable for use as the warp of the anisotropic textile described above, and high strength carbon fibers having a tensile strength of 4 GPa or more are preferable. Examples of the sheet material comprising reinforcement fibers used in the present invention include, for example, woven cloth, unidirectionally oriented sheets, non-woven cloth, mats and the like comprising such reinforcement fibers, combinations of these, and such sheet materials comprising the reinforcement fibers into which the acrylic system resin described hereinbelow has been impregnated; anisotropic textiles are preferably employed.
In particular, in the present invention, a material (a) in which fibers are disposed so as to cross a sheet material in which reinforcement fibers are arranged in one direction is preferable for use as the sheet material comprising reinforcement fibers in which the reinforcement fibers are oriented in one direction and restricted in the horizontal direction; a material (b) in which heat-fusible fibers are disposed, with gaps within a range of 3-15 mm along the longitudinal direction of the reinforcement fibers, in a direction perpendicular to that of the reinforcement fibers in at least one surface of a sheet material in which reinforcement fibers are arranged in one direction, and these are heat-fused, is preferable for use as the sheet material comprising reinforcement fibers; and a material (c) in which a heat-fusible fiber cloth comprising thermoplastic resin, or comprising a web-shaped support body or net-shaped support body covered with thermoplastic resin, is heat-fused to at least one surface of a sheet material arranged in one direction, is preferable for use as the sheet material comprising reinforcement fibers.
Here, material (a) disclosed above is produced by disposing reinforcement fibers as the warp, and reinforcement fibers or other fibers, such as polyamide fibers, acrylic fibers, or fibers resulting from placing acrylic system resins or methacrylic system resins in a fiber shape, as the weft; in other words, from weaving or twining these.
Furthermore, material (b) is produced by arranging reinforcement fibers in a single direction as a sheet, disposing heat-fusible fibers along the width direction of the reinforcement fibers, and heat-fusing these. What is meant by the heat-fusible fibers employed here are fibers which melt and exhibit adhesive properties at temperatures above room temperature, or fibers which are coated on the surfaces thereof with substances which exhibit heat-fusing properties, or threads resulting from an intertwining of heat-fusible fibers and non-heat-fusible fibers, or a combination of any of these fibers. Examples thereof include fibers of polyethylene, polypropylene, polyamide, or acrylic or methacrylic system resins, as well as fibers resulting from a lightly heat-fusible finishing on such fibers, and fibers in which a substance which is heat-fusible such as polyamide or the like is deposited on the surface of fibers such as glass fibers or the like, or fibers resulting from an intertwining of fibers such as glass fibers and nylon threads; however, these fibers are not necessarily limited to these examples. What is meant by the arrangement of the fibers in this case may be the simple placement of the fibers in the surface, or the weaving or intertwining of strengthening fibers as the warp and heat-fusible fibers as the weft.
After the heat-fusible fibers are arranged, it is possible to obtain material (b) by heating these and causing a fusion with the reinforcement fibers.
Among these, the anisotropic textile described above employing a sheet material comprising reinforcement fibers is more preferably employed.
Additionally, material (c) above may be produced by heat-fusing a heat-fusible fiber cloth comprising a thermoplastic resin exhibiting melting and adhesive properties at temperatures above room temperature, or comprising a web-shaped support or net-shaped support body covered with thermoplastic resin, to at least one surface of a sheet-form material in which reinforcement fibers are arranged in one direction.
Examples of the heat-fusible fibers include fibers comprising polypropylene, polyamide, acrylic resin, methacrylic resin, or the like; and the net aperture of the net-shaped support body is preferably wider from the point of view of the impregnation of the resin, so that it is preferable that one polygonal side of the aperture portion be 1 mm or greater, and the surface area of the aperture should be 10 mm2 or more. It is more preferable if one side has a length of 2.5 mm or more, while the aperture surface area is 15 mm2 or more. On the other hand, from the point of view of preventing the loosening of the reinforcement fibers and the handling properties during cutting, it is preferable that the aperture be small, so that it is preferable that one side have a length of 20 mm or less and the aperture surface area be 500 mm2 or less.
What is meant by a web-shaped support body is a sheet material resulting from an intertwining of short fibers or long fibers.
From the point of view of maintenance of interlayer shear strength and resin permeability among the mechanical properties of the substance obtained, it is preferable that the net- or web-shaped support body have a weight of 20 g/m2 or less.
With respect to the materials employed in the fibers used for restricting the reinforcement fibers or the fusible fiber cloth or the like, the use of materials having good adhesive properties with the resin which is impregnated is preferable, so that after curing, superior strength and reinforcement effects can be generated.
When carbon fibers are employed as the reinforcement fibers, optimal carbon fibers for use in the sheet material should preferably be within a range of 100-800 g/m2, and more preferably within a range of 150-600 g/m2.
When the weight is less than 100 g/m2, although the impregnation of the resin is satisfactory, the handling properties of the sheet material worsen, and in particular, the trend is towards the generation of slits in the carbon fibers bundles, and the number of layers affixed increases, so that the operation becomes complex. When this is in excess of 800 g/m2, the impregnation of the resin worsens, and this is not desirable.
An explanation will now be given of the reason for the use of a reactive mixture as the resin in the present invention.
The resin which is employed in the present invention exhibits sufficient repair and reinforcement effects in a comparatively short period of time without requiring control of the conditions; it is important that this resin be capable of initiating polymerization even at 5xc2x0 C., and that curing proceed to a level which exhibits sufficient strength in a comparatively short period of time. One benchmark for the time during which curing proceeds to a level exhibiting sufficient strength is a period of 24 hours; however, a period of 6 hours or less is preferable in order to effectively conduct the procedure, and a period of 3 hours or less is even more preferable. On the other hand, from the point of view of feasibility of the process of impregnating resin into the sheet material from the reinforcement fibers, it is necessary that the resin employed have a period of use at room temperature of 10 minutes or more, and preferably 15 minutes or more, and accordingly, a reactive mixture in which a curing reaction proceeds rapidly after the initiation of polymerization, and which is cured with a radical chain reaction, is preferable. The most preferable reactive mixture is a reactive mixture having as chief components thereof the components described hereinbelow, which has a period of use of 30 minutes or more at room temperature, and in which curing progresses to a level at which a sufficient strength is exhibited within a period of 3 hours.
Examples of component (1), a monomer having vinyl groups, include (meth)acrylate, (meth)acrylic acid, styrene, vinyl toluene, vinyl acetate, and the like. From the point of view of reactivity and the weather resistance of the resin after curing, the inclusion of (meth)acrylate as a chief component is preferable. What is indicated here by xe2x80x98(meth)acrylatexe2x80x99 is acrylate and/or methacrylate.
Concrete examples thereof include: (meth)acrylate monomers having one functional group such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-nonyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, 2-dicyclopentenoxyethyl (meth)acrylate, isobornyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxyethoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, (meth)acrylic acid, (meth)acryloyl morpholine and the like; (meth)acrylate monomers with two functional groups such as ethylene glycol di(meth)acrylate, 1,2-propylene glycol di(meth)acrylate, 1,4-heptanediol di(meth)acrylate, 1,6-hexanediol (meth)acrylate, diethylene glycol di(meth)acrylate, neopentylglycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 2-buten-1,4-di(meth)acrylate, cyclohexane-1,4-dimethanol (meth)acrylate, hydrogenated bisphenol A di(meth)acrylate, 1,5-pentane di(meth)acrylate, trimethylolethane di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, trimethylolpropane di(meth)acrylate, dipropylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 2,2-bis-(4(meth)acryloxypropoxyphenyl)propane, 2,2-bis-(4-(meth)acryloxy(2-hydroxypropoxy)phenyl)propane, bis-(2-(meth)acryloyloxyethyl)phthalate, and the like; and (meth)acrylate monomers having three or more functional groups such as trimethylolpropane tri(meth)acrylate, trimethylolpropane ethylene glycol addition product of tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, trisacryloylethyl isocyanurate, and the like.
Among these, particularly preferable concrete examples are those which have good curing properties and low viscosity, including methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, and tetrahydrofurfuryl (meth)acrylate.
These monomers having vinyl groups may be used singly, or two or more may be used concomitantly.
Examples of component (2), the reactive oligomer having vinyl groups, include, in addition to the so-called macromonomers which result from the addition of a (meth)acrylic group to the end of a comparatively low molecular weight (meth)acrylate copolymer, styrene copolymer, or styrene-acrylonitrile copolymer; polyester (meth)acrylate, which is obtained by reacting a polybasic acid such as phthalic acid, adipic acid or the like with a polyhydric alcohol such as ethylene glycol, butanediol or the like, and (meth)acrylic acid; polyester (meth)acrylate containing allyl ether groups, which is obtained by the reaction of a polybasic acid such as phthalic acid, adipic acid or the like with a polyhydric alcohol such as ethylene glycol, butanediol or the like, and an alcohol containing allyl ether groups such as pentaerythritol triallyl ether, trimethylolpropane diallyl ether or the like, and (meth)acrylic acid; polyester containing allyl ether groups, which was obtained by reacting a polybasic acid such as phthalic acid, adipic acid or the like with a polyhydric alcohol such as ethylene glycol, butanediol or the like, and an alcohol containing allyl ether groups such as pentaerythritol triallyl ether, trimethylolpropane diallyl ether or the like; epoxy (meth)acrylate obtained by reacting an epoxy resin with (meth)acrylic acid; epoxy (meth)acrylate containing allyl ether groups, obtained by reacting a polybasic acid such as phthalic acid, adipic acid or the like with an epoxy resin and an alcohol containing allyl ether groups, such as pentaerythritol triallyl ether, trimethylolpropane diallyl ether and the like; urethane (meth)acrylate, which is obtained by reacting polyol, polyisocyanate and a monomer contain hydroxyl groups such as 2-hydroxyethyl (meth)acrylate or the like; urethane (meth)acrylate containing allyl ether groups, obtained by reacting polyol, polyisocyanate and an alcohol containing allyl ether groups such as pentaerythritol triallyl ether, trimethylolpropane diallyl ether or the like, and a monomer containing hydroxyl groups such 2-hydroxyethyl (meth)acrylate or the like; and urethane containing allyl ether groups, obtained by reacting polyol, polyisocyanate and an alcohol containing allyl ether groups such as pentaerythritol triallyl ether, trimethylolpropane diallyl ether or the like.
Preferable among these reactive oligomers are polyester (meth)acrylate containing allyl ether groups, obtained by reacting a polybasic acid, a polyhydric alcohol, an alcohol containing allyl ether groups and (meth)acrylic acid; epoxy (meth)acrylate, obtained by reacting an epoxy resin with (meth)acrylic acid, and epoxy (meth)acrylate containing allyl ether groups, obtained by reacting a polybasic acid, an epoxy resin, an alcohol containing allyl ether groups and (meth)acrylic acid; more preferable is such a reactive oligomer in solution in component (1), and particularly preferable is a reactive oligomer obtained using phthalic acid as the polybasic acid, bisphenol A and/or bisphenol F type epoxy resin having an epoxy equivalent of 970 or less as the epoxy resin, and pentaerythritol triallyl ether as the alcohol containing allyl ether groups. The epoxy equivalent weight of the epoxy resin employed is set to this level because at greater amounts the solubility in component (1) is reduced, and it thus becomes difficult to prepare a uniform resin and to apply and impregnate this resin uniformly into the sheet material comprising reinforcement fibers.
Further examples of component (2), the thermoplastic polymer, include, in addition to polymers or copolymers of (meth)acrylate monomers having one functional group, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl(meth)acrylate, n-nonyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, 2-dicyclopentenoxyethyl (meth)acrylate, isobornyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate, methoxyethoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, (meth)acrylic acid, and (meth)acryloyl morpholine and the like, copolymers of (meth)acrylate monomers and monomers which are copolymerizable with (meth)acrylate monomers such as styrene, polymers of monomers which are copolymerizable with (meth)acrylate monomers, cellulose system macromolecules such as cellulose acetate butyrate, cellulose acetate propionate, and the like, diallyl phthalate resin, epoxy resin, vinyl resins such as vinyl chloride and vinyl acetate resin and the like, and various thermoplastic elastomers; these thermoplastic polymers may be used singly or together. These are preferably employed in solution in component (1), as in the case of the reactive oligomers described above.
Furthermore, in order to improve various properties, it is possible to add a variety of additives, for example, plasticizers, weathering agents, anti-static agents, lubricants, release agents, paints, pigments, anti-foaming agents, polymerization inhibitors, and various types of fillers. In particular, in order to improve air blast effects, and provide gloss to the cured surface, and in order to increase dirt resistance, the addition of paraffins such as paraffin wax, microcrystalline wax, polyethylene wax, and the like, or addition of higher fatty acids such as stearic acid, 1,2-hydroxystearic acid, and the like, is preferable.
No particular restriction is made with respect to the curing catalyst which is used for the polymerization of such reactive mixtures, insofar as this comprises a curing catalyst system which meets the curing conditions, such as the period of use, the polymerization initiation temperature, and the curing period; catalyst systems which are commonly employed as curing catalysts for radical polymerization at room temperature may be used.
Concrete examples thereof include combinations of organic peroxides which are individually stable at room temperature (the temperature at the place of use) such as benzoyl peroxide, methylethylketone peroxide, and the like, and curing promoters which make possible the decomposition of such organic peroxides at room temperatures.
In order to avoid the dangers presented by the handling of benzoyl peroxide, it is preferable that this be used in the form of a paste or a powder in which the concentration is diluted to approximately 50% using an inert liquid or solid.
Examples of curing promoters include metallic soaps such as cobalt naphthenate, cobalt octylate, and the like, as well as aromatic tertiary amines such as dimethyl toluidine, diethyl toluidine, diisopropyl toluidine, dihydroxyethyl toluidine, dimethylaniline, diethyl aniline, diisopropyl aniline, dihydroxyethyl aniline and the like. The curing promoters may be used singly, or two or more may be used concomitantly, however the curing promoters are not limited to these examples.
It is preferable, from the point of view of the coating properties of the resin, the impregnation properties of the resin into a sheet material comprising reinforcement fibers, and the penetration into the concrete structure, that the viscosity of the reactive mixture be within a range of 5-104 centipoise at 20xc2x0 C., and more preferably within a range of 5-800 centipoise.
In the repair and reinforcement method of the present invention, the execution of foundation treatment on the surface of the preexisting structure on which execution is to be conducted, prior to carrying out the repair and reinforcement, is highly desirable in order to obtain sufficient repair and reinforcement effects. This foundation treatment may be conducted by means of a method in which initially, where coating or the like has been carried out on the surface of the structure, this is removed, and the surface is rendered smooth, whereupon cracked portions are filled in with a material having good adhesion properties with the reactive mixture which is employed in the present invention, and where necessary, this is subjected to further abrasion, and the surface is rendered smooth. Furthermore, the application of the reactive mixture employed in the present invention on to the surface on which repair and reinforcement is to be carried out, prior to carrying out the repair and reinforcement method of the present invention, is preferable in order to improve the adhesion properties.
Representative embodied configurations of the repair and reinforcement method of the present invention are given below.
(Embodied Configuration 1)
A reactive mixture in which an organic peroxide and a curing promoter are uniformly mixed is first applied to those portions on which repair and reinforcement is to be carried out, and after a sheet material comprising reinforcement fibers, and preferably an anisotropic textile, has been applied to the surfaces to which the reactive mixture was applied; the same reactive mixture is impregnated from the opposite side, and allowed to cure.
(Embodied Configuration 2)
A repair and reinforcement method for preexisting structures, in which a reactive mixture (liquid A) containing an organic peroxide but not containing a curing promoter is mixed with a reactive mixture (liquid B) containing a curing promoter but not containing an organic peroxide, using a two-liquid mixing-type coater provided with a cleaning pump, the mixed resin liquid is applied to those portions of the preexisting structure which are to be repaired and reinforced, a sheet material comprising strengthening fibers, and preferably an anisotropic textile, is applied to the surfaces to which the resin liquid was applied, liquid A and liquid B are again mixed using the two-liquid mixing-type coater, and the mixed resin liquid is applied to the outer surface of the sheet material comprising reinforcement fibers which was affixed and this resin is then allowed to cure.
(Embodied Configuration 3)
A reactive mixture (liquid A) containing an organic peroxide but not containing a curing promoter is first applied to those portions of the preexisting structure which are to be repaired and reinforced, and then a sheet material comprising reinforcement fibers, and preferably an anisotropic textile, is affixed thereto, whereupon a reactive mixture (liquid B) containing a curing promoter but not containing an organic peroxide is impregnated, and by means of the contact and mixture of liquid A and liquid B, curing is carried out.
Alternatively, liquid B may first be applied to those portions of the preexisting structure which are to be repaired and reinforced, a sheet material comprising reinforcement fibers, and preferably an anisotropic textile, is then affixed, whereupon liquid A is impregnated, and as a result of the contact and mixture of liquid A and liquid B, curing is carried out. The adoption of such a method is particularly desirable when a sufficient reactive mixture period of use is to be guaranteed. Liquid A and liquid B may of course be used in reverse order.
(Embodied Configuration 4)
A compound comprising the curing promoter of the reactive mixture may be deposited in advance on the sheet material comprising reinforcement fibers, and preferably on an anisotropic textile, and during execution, a reactive mixture which contains an organic peroxide but does not contain a curing promoter may be impregnated, initiating polymerization, and this may then be allowed to cure.
Alternatively, an organic peroxide may be applied in advance to the sheet material comprising reinforcement fibers, preferably an anisotropic textile, and during execution, this may be impregnated with a reactive mixture which contains a curing promoter but does not contain an organic peroxide, initiating polymerization, and thus carrying out curing.
(Embodied Configuration 5)
A reactive mixture (liquid A) which contains an organic peroxide but does not contain a curing promoter is first applied to those portions of the preexisting structure which are to be repaired and reinforced, and then a sheet material comprising reinforcement fibers, preferably an anisotropic textile, is affixed, and thereafter a reactive mixture (liquid B) which contains a curing promoter but does not contain an organic peroxide is impregnated, and on this, liquid A is again impregnated, and as a result of the contact and mixture of liquid A and liquid B, curing is carried out.
Alternatively, liquid B may first be applied to those portions of the preexisting structure which are to repaired and reinforced, a sheet material comprising reinforcement fibers, preferably an anisotropic textile, is affixed, and thereafter liquid A is impregnated, whereupon liquid B is impregnated, and as a result of the contact and mixture between liquid A and liquid B, curing is carried out. The adoption of this method is particularly desirable in cases in which a sufficient period of use is to be guaranteed for the reactive mixture, and in which a cured state which is more complete than a state in which there are few curing deficiency spots is desired.
In the repair and reinforcement method in accordance with the present invention, no particular restriction is made with respect to the method by which reactive mixtures are applied to the portions of the preexisting structures which are to be repaired and reinforced, or to the sheet material comprising reinforcement fibers; however, it is preferable that this be carried out in a short period of time by using a common spray gun, a two-liquid internal-mixing-type spray gun containing a static mixer, or a two-liquid external-mixing-type spray gun.
Next, the anisotropic textile will be explained; this is preferably employed as the sheet material comprising reinforcement fibers of the method for repair and reinforcement of preexisting structures described above, and is also preferably employed in conventional repair and reinforcement methods.
In order to effectively conduct the repair and reinforcement of preexisting structures, the use of a sheet material in which the high strength and highly elastic fibers employed are arranged in a single direction is important; however, a sheet material resulting solely from such arrangement cannot be handled, and is incapable of use as the material for repair and reinforcement. The so-called prepreg method, in which resin is impregnated in advance, is the most common method used to guarantee sufficient handling properties for use as a repair and reinforcement material; however, because the resin which cures at ordinary temperatures which is employed in such repair and reinforcement methods cures if it is not used immediately after impregnation, such resin is inappropriate for use as the matrix resin used in prepregs, and the common matrix resin for use in prepregs must be heated to a high temperature of over 100xc2x0 C. in order to be cured, so that such resin is also inappropriate for use in the repair and reinforcement method for preexisting structures. For this reason, a method is commonly employed in which the amount of resin impregnated in advance is set to the lower limit necessary to guarantee the handling properties, and moreover, a curing agent is not contained so as to guarantee the period of use, and during execution, curing is conducted using a room-temperature-curing agent contained within a relatively large amount of resin which is additionally impregnated; however, the resin which is impregnated during execution is restricted to the same type of resin as that which was applied in advance, and it is necessary to apply a slightly greater amount than the standard amount of sizing agent in order to guarantee the handling properties during execution, so that the impregnation properties of the resin which is impregnated during execution decline dramatically. Furthermore, in order to improve the handling properties during execution, it is common to attach a planar support body such a non-woven cloth or a net type textile or the like via a resin applied to the reinforcement fibers, or an adhesive layer which is specially provided between a planar support body and the reinforcement fibers; however, although the handling properties improve, the impregnation properties of the resin during execution decline even more.
The anisotropic textile of the present invention does not involve the application of resin to the high strength and highly elastic fibers which are arranged in a single direction, so that there are no restrictions on the type of resin which may be impregnated during execution, and the impregnation properties are very good. In particular, resin which polymerizes and cures rapidly even at low temperatures may be employed as the matrix resin, so that there is no limitation of the environmental conditions during execution, and it is possible achieve a great shortening of the execution time. Furthermore, since this textile employs composite threads for the weft which have a lower tensile elastic modulus than that of the warp, and after weaving, the textile is heated to a temperature above the melting point of the low melting point fibers forming the composite threads and the weft and warp are appropriately adhered, the handling properties during execution are extremely good, and problems such as a disarrangement of the orientation of the fibers during execution, and a decrease in the reinforcement effect, do not occur.
In the present invention, it is possible to employ fibers which are commonly employed as reinforcement fibers as the fibers used in the warp, so that inorganic fibers such as carbon fibers or the like, and organic fibers such as aramide fibers or the like, may be employed; however, high strength and highly elastic fibers having a tensile strength of 3 GPa or more and a tensile elastic modulus of 150 GPa or more are preferable. High strength carbon fibers having a tensile strength of 4 GPa or more are particularly preferable as they provide superior reinforcement effects.
In the present invention, a composite thread comprising two types of fibers having a melting point difference of 50 xc2x0 C. or more is used as the weft. The fiber with the high melting point in the composite thread is the basic weft; this functions as the weft at least until the end of execution. Accordingly, a certain amount of strength and elastic modulus is required; however, the tensile elastic modulus must be less than that of the warp. When the tensile elastic modulus is greater than that of the warp, the warp tends to drift in the longitudinal direction, and sufficient tensile strength is not attained. The preferred tensile elastic modulus range of the weft is 50-100 GPa. Furthermore, in order to prevent a disordering of the orientation of the fibers during execution, it is very important that this does not dissolve in the resin which forms the matrix resin. Examples of such high melting point fibers include glass fibers; however, these fibers are not necessarily limited to this example.
The low melting point fibers are fibers which are necessary in order to cause the warp and weft to become unitary after weaving and in order to provide superior handling properties. Without these low melting point fibers, a disordering of the fibers during handling is likely to occur, and sufficient reinforcement effects cannot be obtained. Examples of these low melting point fibers include low melting point polyamide fibers, polyester fibers, and polyolefin fibers; however, these fibers are not necessarily restricted to these examples.
The two types of fibers described above are necessary components of the composite threads which are employed in the weft; however, in order to improve the handling properties during execution by unifying these two types of fibers and strengthening the adhesion between the warp and weft prior to the impregnation of resin, it is preferable to use composite threads to which have been applied 0.5-10 weight percent of a high molecular compound which melts or softens at a temperature of 100xc2x0 C. or less. The high molecular compound which is deposited is not particularly restricted insofar as it is a compound which melts or softens at a temperature of 150xc2x0 C. or less; however, compounds which are water-soluble or are capable of forming an aqueous emulsion are preferable, since they facilitate the process of deposition onto the composite threads. Examples of such high molecular compounds include polyvinyl acetate, ethylene-vinyl acetate copolymer, vinyl acetate-acrylic copolymer, polyacrylic ester, polyester, polyethylene, and polybutadiene system copolymers; however, these compounds are not necessarily limited to the examples given.
The low melting point fibers used in the weft of the present invention and the high molecular compound which melts or softens at temperatures of 150 xc2x0 C. or less contribute to the superior handling properties of the anisotropic textiles; however, from the point of view of the mechanical properties after curing, particularly the generation of tensile strength, it is desirable that the restriction of the warp by the weft be weak. Accordingly, it is desirable to choose low melting point fibers and a high molecular compound which gradually change to a non-adhesive state as a result of the reactive mixture impregnated during execution, and to control the amount of high molecular compound deposited. In particular, it is preferable that the high molecular compound be somewhat soluble in the reactive mixture which is impregnated during execution, and it is desirable that this compound be selected in concert with the reactive mixture which is impregnated.
Furthermore, from the point of view of providing strength after curing, it is desirable that the weft be as thin as possible, so that the weight per meter of the fiber is preferably 0.1 g or less, and more preferably within a range of 0.01-0.05 g.
The preferable ratio of the high melting point fibers and the low melting point fibers in the composite threads is such that, in volumetric ratio, with respect to one unit of high melting point fibers, the low melting point fibers should be within a range of 0.25-2.0, and a range of 0.5-1.5 is more preferable from the point of view of the adhesive properties and the mechanical properties.
The weft spacing in the anisotropic textile of the present invention is within a range of 3-15 mm. When the spacing is less than 3 mm, the drift of the warp in the longitudinal direction cannot be ignored, and sufficient tensile strength will not be attained after curing of impregnation resin, while when the spacing is greater than 15 mm, the handling properties of the sheet material worsen, and this is not desirable. A more preferable weft spacing range is 4-10 mm.
Any resin may be employed as the resin which is used in combination with the anisotropic textile insofar as it obtains sufficient repair and reinforcement effects, is easily impregnated into the anisotropic textile at room temperatures, and exhibits sufficient strength after curing; however, in order to produce sufficient repair and reinforcement effects in a comparatively short period of time without controlling the environmental conditions, it is necessary to employ a resin which initiates polymerization even at 5xc2x0 C., and in which curing proceeds to a level which exhibits sufficient strength in a comparatively short period of time. It is possible to use 24 hours as a period during which curing proceeds to a level which is exhibits sufficient strength; however, a period of 6 hours or less is preferable in order to efficiently conduct operations, and a period of 3 hours or less is even more preferable. On the other hand, from the point of view of facilitating the operation in which the resin is impregnated into the anisotropic textile, it is necessary that the resin which is employed have a period of use which is 10 minutes or greater, and preferably 15 minutes or greater, at room temperatures, and accordingly, the reactive mixtures described above, in which the curing reaction proceeds rapidly after the initiation of polymerization, and curing is conducted with a radical chain reaction are preferable. The most preferable reactive mixture is one which has a period of use of 30 minutes or more at room temperature and in which curing proceeds to a level which exhibits sufficient strength within a period of 3 hours.